Process for the preparation of 1,1&#39;-diacetals

ABSTRACT

The invention relates to a process for the synthesis of 1,1&#39;-diacetals, which method is also suitable for the stereoselective synthesis of glycosides with the 1,1&#39;-diacetal structure. The process involves reacting a silyl compound of formula (II) with an acetal of formula (III) in the presence of a catalyst of formula (IV) or (V) in a suitable solvent.

The present invention relates to an unobvious process for the production of certain 1,1'-diacetals.

The stereoselective formation of glycosides is one of the most demanding synthetic problems in the chemistry of natural products (G. Wulff and G. Rohle, Angew. Chem. 86, 173 (1974); Angew. Chem. Int. Ed. Engl. 13, 157 (1974)). In this respect, the synthesis of glycosides with the 1,1'-diacetal structure, as present in the 1,1-linked disaccharides or iridoid-glycosides (L.-F.Tietze and U. Niemeyer, Chem. Ber. 111, 2,423 (1978); L.-F. Tietze, U. Niemeyer, P. Marx, K.-H. Glusenkamp and L. Schwenen, Tetrahedron 36, 735 (1980); and L.-F. Tietze, U. Niemeyer, P. Marx and K.-H. Glusenkamp, Tetrahedron 36, 1,231 (1980)), is particularly difficult.

A surprisingly simple method for the synthesis of certain 1,1'-diacetals has now been found, which method is suitable, inter alia, also for the stereoselective synthesis of glycosides with the 1,1'-diacetal structure.

According to the present invention, there is provided a process for the production of a 1,1'-diacetal of the formula ##STR1## in which

R¹ and R², which are identical or different, represent an optionally substituted aliphatic saturated or unsaturated hydrocarbon radical, it being possible for R¹ and R² to be bonded to each other,

R³ represents an optionally substituted alkyl radical and

R⁴ represents an optionally substituted O-alkyl radical or an optionally substituted, saturated or unsaturated, aliphatic radical, in which a silyl compound of the formula ##STR2## in which

R¹ and R² have the abovementioned meanings and

R⁶, R⁷ and R⁸, are identical or different and represent an optionally substituted alkyl radical, is reacted with an acetal of the formula ##STR3## in which

R³ and R⁴ have the abovementioned meanings, and

R⁵ represents an optionally substituted alkyl or phenyl radical, in the presence of a catalyst of the formula ##STR4## in which

R⁹, R¹⁰, R¹¹, R¹² and R¹³, which are identical or different, represent an alkyl radical having 1 to 8 carbon atoms, and

X represents FSO₃, CF₃ CO₂, ClO₄, BF₄, CH₃ SO₃ or CF₃ (CF₂)_(n) --SO₃ (in which n is 0, 1, 2, 3 or 4), in a suitable solvent.

Silyl compounds of formula (II), used as starting materials are in themselves known (see inter alia, L. Birkofer, A. Ritter and F. Bentz, Chem. Ber. 97, 2,I96 (1964); and A. Klemmer, E. Buhe and R. Kutz, Liebigs Ann. Chem. 739, 185 (1970)).

Preferred 1,1'-diacetals of formula (I) produced by the process of the present invention are those, in which

R¹ and R², which are identical or different, denote an aliphatic, saturated or unsaturated hydrocarbon radical having 1 to 6 carbon atoms (optionally substituted by 1 to 6, especially 1, 2 or 3 substituents preferably selected from (protected) OH, O-alkyl, preferably having 1 to 4 carbon atoms, alkoxycarbonyl, preferably having 1 to 4 carbon atoms in the alkoxy portion and phenyl), or

R¹ and R² together represent an alkylene radical preferably having 3 or 4 carbon atoms, which can be optionally substituted as indicated immediately above,

R³ denotes an optionally substituted alkyl radical having 1 to 6 carbon atoms, and

R⁴ denotes an optionally substituted O-alkyl radical having 1 to 6 carbon atoms, or an optionally substituted, saturated or unsaturated, aliphatic radical having 1 to 6 carbon atoms (preferred substituents for R³ and R⁴ being 1 to 6, especially 1, 2 or 3 substituents, preferably selected from those mentioned for R¹ and R², and halogen).

Preferred starting materials of formula (III) are those, in which

R³ and R⁴ have those meanings given above for those radicals, and

R⁵ denotes an optionally substituted alkyl radical having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, or a phenyl radical optionally substituted by halogen, nitro or O-alkyl (preferably having 1 to 4 carbon atoms).

Preferred starting materials of formula (II) are those, in which

R¹ and R² have those meanings given above for these radicals, and

R⁶, R⁷ and R⁸, which are identical or different denote an alkyl radical having 1 to 8 (particularly 1-4) carbon atoms, especially a methyl radical.

Preferred catalysts of formula (IV) or (V) are those in which R⁹, R¹⁰, R¹¹, or R¹² and R¹³, are identical or different and denote an alkyl radical having 1 to 8 (particularly 1 to 4) carbon atoms, especially a methyl radical and X has the abovementioned meaning, especially CF₃ SO₃.

Particularly preferably all of the radicals R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹² and R¹³ denote methyl radicals.

In a particularly preferred mode of the invention the compound (II) represents a compound of the formula (VI) ##STR5## wherein R¹⁹ -R²² are the same or different and represent a protective group for OH-group.

Most preferably, the radicals OR¹⁹ -OR²¹ and the radical CH₂ --OR²² together with the basic ring system are in a glucose-configuration.

The customary protective groups, such as acetyl, benzyloxycarbonyl, benzyl or trityl, are suitable OH protective groups on the abovementioned (protected) OH substituent.

In carrying out the reaction the silyl compound of formula (II) is preferably reacted with equimolar amounts or an excess of the compound of formula (III). Preferably about 1/10 equivalent of the catalyst of formula (IV) or (V) relative to the silyl compound of formula (II) is used.

Preferred solvents for the reaction according to the present invention are CH₂ Cl₂, CHCl₃, acetonitrile, diethyl ether or tetrahydrofuran.

The reaction is carried out within a wide temperature range, preferably at a temperature between -80° C. and 100° C. If the reaction is carried out in a temperature range between -80° and -40° C., a compound of formula (I) is formed with retention of the configuration at C-1, whereas at 0° to 100° C. inversion occurs.

EXAMPLES

The equations which follow illustrate the reactions tabulated below. The description and the tables refer to the numbers below the formulae. Where a formula does not define a single compound, the individual compounds are referred to by the number and a lower case letter. The identity of those individual compounds are indicated in Table 1.

    __________________________________________________________________________                              Product                                                                        (obtain from Reactants                                                         with indicated spec-                                  Reactant 1Reactant 2     ific radical meanings)                                __________________________________________________________________________                               ##STR6##                                              ##STR7##                                                                                                ##STR8##                                             R.sup.16 = Ac, Bn R.sup.14 =  H; R.sup.15 = OSi(CH.sub.3).sub.3 or             R.sup.14 = OSi(CH.sub.3).sub.3 ; R.sup.15 = H                                                            ##STR9##                                             __________________________________________________________________________

Above and hereinafter, the abbreviations used have the following meanings:

Me=Methyl

Ac=Acetyl

Bn=Benzyl

Ph=Phenyl

R¹⁷, R¹⁸ ##STR10##

The acetals (2) which are used for the preparation of the products (3) and (4) can be replaced by the respective aldehyds (11) and methyl-trimethylsilyl ether (12) (c.f. T. Tsunoda et al., Tetrahedron Letters 1980, 1357).

The yields of compounds (3) and (4) so obtained are comparable or better than those listed in Table 2. ##STR11##

Examples for R are CH₂ --C₆ H₅, n--C₃ H₇, CH₂ OCH₃ and CH₂ Cl.

GENERAL PROCEDURE

To a solution of 0,25 mmol silylcompound (1), 0,25 mmol aldehyde (11) and 0,35 mmol methyl-trimethylethyl-silyl ether (12) in 2 ml dry CH₂ Cl₂ 0,2 ml of a 0,1 molar solution of trimethylsilyl-trifluoromethan sulfonate in CH₂ Cl₂ are added at -70° C. and under inert atmosphere. The mixture is stirred for 20-60 hours at this temperature. The reaction can be surveyed by DC with silicagel and hexan/ethyl acetate 1:1 (V/V) as running agent.

It has further been found that a significant increase of the reaction velocity can be achieved in the acetalisation, if about 0,5 mol equivalents of aceton based on e.g. trimethylsilylglucose are added.

    ______________________________________                                         Reactant 1 R.sup.16   R.sup.14 R.sup.15                                        ______________________________________                                         1a         Ac         OSiMe.sub.3                                                                             H                                               1b         Ac         H        OSiMe.sub.3                                     1c         Bn         OSiMe.sub.3                                                                             H                                               1d         Bn         H        OSiMe.sub.3                                     Reactant 2    R.sup.5 R.sup.4                                                  ______________________________________                                         2a            Me      H                                                        2b            Ph      H                                                        2c            Me      CH.sub.2 Ph                                              2d            Me      n-C.sub.3 H.sub.7                                        2e            Me      CH.sub.2 --CH(OMe).sub.2                                 2f            Me      CH.sub.2 --OMe                                           2g            H       CH.sub.2 Cl                                              2h            Me      CH.sub.2 Br                                              2i            Me      OMe                                                      ______________________________________                                         Product        R.sup.4                                                         ______________________________________                                         3a          4a     H                                                           3b          4b     CH.sub.2 Ph                                                 3c          4c     n-C.sub.3 H.sub.7                                           3d          4d     CH.sub.2 --CH(OMe).sub.2                                    3e          4e     CH.sub.2 --OMe                                              3f          4f     CH.sub.2 Cl                                                 3g          4g     CH.sub.2 Br                                                 3h                 OMe                                                         ______________________________________                                         Product      R.sup.17   R.sup.18                                               ______________________________________                                         5a           H          OCH.sub.2 --OMe                                        5b           OCH.sub.2 --OMe                                                                           H                                                      ______________________________________                                    

The reactions were carried out according to the following instructions.

(A) 0.2 ml of a 0.1 molar solution of trimethylsilyl trifluoromethanesulphonate in dichloromethane is added to a solution of 0.25 mmol of the silyl compound (1 or 7) and 0.50 mmol of the acetal (2) in 3 ml of anhydrous dichloromethane at -70° C., under an inert gas atmosphere, and the mixture is stirred at this temperature for from 20 to 60 hours. The course of the reaction can be followed by thin layer chromatography on silica gel (mobile phase: hexane/ethyl acetate 1:1).

(B) 0.1 ml of a 0.1 molar solution of trimethylsilyl trifluoromethanesulphonate in dichloromethane is added to a solution of 0.25 mmol of the silyl compound (1) and 0.50 mmol of the acetal (2) in 5 ml of anhydrous dichloromethane at 0° C., under an inert gas atmosphere, and the mixture is stirred at this temperature for from 4 to 16 hours. The course of the reaction can be followed by thin layer chromatography on silica gel (mobile phase: hexane/ethyl acetate 1:1).

(C) 0.2 ml of a 0.1 molar solution of trimethylsilyl trifluoromethanesulphonate in dichloromethane is added to a solution of 105 mg (0.25 mmol) of the silyl compound (1a) and 53.0 mg (0.50 mmol) of methyl orthoformate (2i) in 3 ml of anhydrous dichloromethane at -30° C., under an inert gas atmosphere, and the mixture is stirred at this temperature for approx. 40 hours. After working up, 70 mg of a mixture of (3h) and (6) are obtained.

(D) 42.4 mg (0.2 mmol) of (9) are reacted with 84.0 mg (0.2 mmol) of (1) (α,β mixture), according to method C (reaction time 6 days). 93.8 mg (89%) of the isomeric glucoside (10) are obtained. The product is identified by comparison with original substances.

WORKING-UP

To work up the reaction mixture, 0.1 ml of triethylamine are added and the mixture is washed with saturated NaHCO₃ solution and NaCl solution and dried over Na₂ SO₄ /Na₂ CO₃ (1:1). After the solvent has been evaporated off in vacuo, the product obtained consists almost of a single substance, and can be chromatographed over silica gel for further purification.

(Z) To determine the configuration at C-1, the tetraacetates (3 and 4) were converted solvolytically, using methanol/sodium methanolate, into the free glucosides.

Table 2 below shows the reactants employed, the procedure, the yields and the products and their characterisation.

                                      TABLE 2                                      __________________________________________________________________________                           Yield                        Analysis                    Reactants                                                                            Method                                                                              Product    (%) .sup.1 H--NMR (δ = ppm)                                                                 IR        Calculated                                                                             Found               __________________________________________________________________________     1a + 2a                                                                              A    1-O--(1'-methoxy-                                                                         75  (100 MHz, CDCl.sub.3):                                                                        (KBr):    C: 48.98                                                                               49.09               1a + 2b                                                                              A    methyl)-2,3,4,6-                                                                          88  1.97 (s, 3H, CH.sub.3),                                                                       2990, 2960                                                                               H: 6.17 6.19                           tetra-O--acetyl-                                                                              2.01 (s, 6H, CH.sub.3),                                                                       2920 (CH),                                                                               C.sub.16 H.sub.24                                                              O.sub.11                               β-D-glucopyran-                                                                          2.05 (s, 3H, CH.sub.3),                                                                       2840      (392.36)                               ose (3a)       3.35 (s, 3H, OCH.sub.3),                                                                      (acetal)                                                        3.69 (m, 1H, 5-H),                                                                            1760, 1745                                                      4.05 (d, d J = 12 Hz                                                                          (CO)                                                            and 2.5 Hz, 1H, 6-H),                                                          4.28 (d, d J = 12 Hz                                                           and 4.5 Hz, 1H, 6-H),                                                          4.50-5.13 (m, 6H, 1-H,                                                         1-H, 2-H, 3-H, 4-H)                                        Z    1-O--(1'-methoxy-                                                                             (80 MHz, D.sub.6 -acetone/                                      methyl)-β-D-glu-                                                                         D.sub.2): 3.20-4.00 (m,                                         copyranose     6H, 2-H, 3-H, 4-H, 5-H,                                                        6-H), 3.46 (s, 3H, OCH.sub.3),                                                 4.45 (s, 4H, OH), 4.58                                                         (d, J = 7.5 Hz, 1H, 1-H),                                                      4.73 (d, J = 6.5 Hz, 1H,                                                       1'-H) 5.02 (d, J = 6.5 Hz,                                                     1H, 1'-H)                                            1b + 2b                                                                              A    1-O--(1'-methoxy-                                                                         87  (100 MHz, CDCl.sub.3):                                          methyl)-2,3,4,6-                                                                              1.99 (s, 3H, CH.sub.3),                                         tetra-O--acetyl-                                                                              2.01 (s, 3H, CH.sub.3),                                         α-D-glucopyran-                                                                         2.04 (s, 3H, CH.sub.3),                                         ose (4a)       2.07 (s, 3H, CH.sub.3),                                                        3.38 (s, 3H, OCH.sub.3),                                                       3.99-4.35 (m, 3H, 5-H,                                                         6-H), 4.54-5.60 (m,                                                            6H, 1'-H, 1-H, 2-H,                                                            3-H, 4-H)                                                  Z    1-O--(1'-methoxy-                                                                             (80 MHz, D.sub.6 -acetone/                                      methyl)-α-D-glu-                                                                        D.sub.2): 3.50-4.00 (m,                                         copyranose     6H, 2-H, 3-H, 4-H, 5-H,                                                        6-H), 3.55 (s, 3H, OCH.sub.3),                                                 4.20 (s, 4H, OH), 4.75                                                         (d, J = 6.5 Hz, 1H, 1'-H),                                                     5.03 (d, J = 6.5 Hz, 1H,                                                       1'-H), 5.17 (d, J = 3.75 Hz,                                                   1H, 1-H)                                             1a + 2c                                                                              A    1-O--(1'-methoxy-                                                                         84  (100 MHz, CDCl.sub.3): 2.01                                                                   (KBr):                                           2'-phenyl-ethyl-                                                                              (s, 3H, CH.sub.3), 2.04 (s,                                                                   3030 (CH                                         2,3,4,6-tetra-O--                                                                             3H, CH.sub.3), 2.06 (s, 3H,                                                                   aromatic)                                        acetyl-β-D-gluco-                                                                        CH.sub.3), 2.08 (s, 3H,                                                                       2980, 2960                                       pyranose (3b)  CH.sub.3), 2.90-3.03 (m,                                                                      2940 (CH                                                        2H, 2'-H), 2.35 and                                                                           aliphatic)                                                      2.40 (s, 3H, OCH.sub.3),                                                                      2840                                                            3.60-3.85 (m, 1H,                                                                             (acetal)                                                        5-H), 4.06-4.33 (m,                                                                           1745 (CO)                                                       2H, 6-H), 4.71-5.19                                                            (m, 5H, 1'-H, 1-H,                                                             2-H, 3-H, 4-H), 7.27                                                           (m, 5H, C.sub.6 H.sub.5)                                   Z    1-O-(1'-methoxy-                                                                              (100 MHz, D.sub.6 -acetone/                                                                             C: 57.32                                                                               57.41                          2'-phenyl-ethyl)-                                                                             D.sub.2 O): 2.95-3.08 (m,                                                                               H: 7.06 7.08                           β-D-glucopyranose                                                                        2H, 2'-H), 3.32-3.56     C.sub.15 H.sub.22                                                              O.sub.7                                               (m, 4H, 2-H, 3-H,        (314.33)                                              4-H, 5-H), 3.37 and                                                            3.39 (2s, 3H, OCH.sub.3),                                                      3.60-3.98 (m, 2H,                                                              6-H), 4.29 (s, 4H,                                                             OH), 4.57 and 4.67                                                             (2d, J = 7.5 Hz, 1H,                                                           1-H), 4.87 and 5.03                                                            (2d, d, J = 7 Hz and                                                           4 Hz, 1H, 1'-H), 7.27                                                          (m, 5H, C.sub.6 H.sub.5)                             1a + 2c                                                                              B    1-O--(1'-methoxy-                                                                         72  (80 MHz, CDCl.sub.3):                                           2'-phenyl-ethyl)-                                                                             2.00 (s, 3H, CH.sub.3),                                         2,3,4,6-tetra-O--                                                                             2.02 (s, 3H, CH.sub.3),                                         acetyl-α-D-gluco-                                                                       2.04 (s, 3H, CH.sub.3),                                         pyranose (4b)  2.07 (s, 3H, CH.sub.3),                                                        2.87-3.07 (m, 2H,                                                              2'-H), 3.35 and 3.37                                                           2s, 3H, OCH.sub.3), 3.55                                                       (d, d, J = 12.5 Hz                                                             and 2.5 Hz, 1H, 6-H),                                                          3.87 (d, d, j = 12.5 Hz                                                        and 3.75 Hz, 1H,                                                               6-H), 4.02-4.25 (m,                                                            1H, 5-H), 4.6-5.63                                                             (m, 5H, 1'-H, 1-H,                                                             2-H, 3-H, 4-H), 7.25                                                           (m, 5H, C.sub.6 H.sub.5)                                   Z    1-O--(1'-methoxy-                                                                             (80 MHz, D.sub.6 -acetone/                                      2'-phenyl-ethyl)-                                                                             D.sub.2 O): 2.98 (d, J =                                        α-D-glucopyranose                                                                       5.5 Hz, 2H, 2'-H),                                                             3.1-3.8 (m, 6H, 2-H,                                                           3-H, 4-H, 5-H, 6-H),                                                           3.37 and 3.39 (2s,                                                             3H, OCH.sub.3), 3.89 (s,                                                       4H, OH), 4.91 (t,                                                              J = 5.5 Hz, 1H,                                                                1'-H), 5.09 (d, J =                                                            3.75 Hz, 1H, 1-H),                                                             7.25 (m, 5H, C.sub.6 H.sub.5)                        1a + 2d                                                                              A    1-O--(1'-methoxy-                                                                         78  (100 MHz, CDCl.sub.3):                                                                        (Film)    C: 52.53                                                                               52.60                          butyl)-2,3,4,6-                                                                               0.95 (t, J = 7 Hz,                                                                            2960, 2940                                                                               H: 6.96 7.01                           tetra-O--acetyl-                                                                              3H, 4'-H) 1.22-1.82                                                                           2880 (CH) C.sub.19 H.sub.30                                                              O.sub.11                               β-D-glucopyran-                                                                          (m, 4H, 2'-H, 3'-H),                                                                          2840      (434.44)                               ose (3c)       2.01 (s, 3H, CH.sub.3),                                                                       (acetal)                                                        2.04 (s, 6H, CH.sub.3),                                                                       1745 (CO)                                                       2.08 (s, 3H, CH.sub.3),                                                        3.31 and 3.37 (2s,                                                             3H, OCH.sub.3), 3.62-3.80                                                      (m, 1H, 5-H), 4.08-                                                            4.34 (m, 2H, 6-H),                                                             4.49-5.34 (m, 5H,                                                              1'-H, 1-H, 2-H, 3-H,                                                           4-H)                                                       Z    1-O--(1'-methoxy-                                                                             (100 MHz, D.sub.6 -acetone/                                     butyl)-β-D-gluco-                                                                        D.sub.2 O): 0.89 (t, J =                                        pyranose       7.0 Hz, 3H, 4'-H),                                                             1.14-1.80 (m, 4H,                                                              2'-H, 3'-H), 3.18-                                                             3.54 (m, 4H, 2-H, 3-H,                                                         4-H, 5-H), 3.38 and                                                            3.42 (2s, 3H, OCH.sub.3),                                                      3.66 (d, d, J = 12.5 Hz                                                        and 2.5 Hz, 1H,                                                                6-H), 3.86 (d, d, J =                                                          12.0 Hz and 2.0 Hz,                                                            1H, 6-H), 4.05 (s,                                                             4H, OH), 4.47 and                                                              4.59 (2d, J = 7.5 Hz,                                                          1H, 1-H), 4.64 and                                                             4.83 (2t, J = 5.0 Hz,                                                          1H, 1'-H)                                            1a + 2d                                                                              B    1-O--(1'-methoxy-                                                                         57  (60 MHz, CDCl.sub.3):                                           butyl)-2,3,4,6-                                                                               0.80-1.60 (m, 7H,                                               tetra-O--acetyl-                                                                              2'-H, 3'-H, 4'-H),                                              α-D-glucopyran-                                                                         1.92 (s, 3H, CH.sub.3),                                         ose (4c)       1.94 (s, 3H, CH.sub.3),                                                        1.96 (s, 3H, CH.sub.3),                                                        2.00 (s, 3H, CH.sub.3),                                                        3.23 and 3.34 (2s,                                                             3H, OCH.sub.3), 3.89-4.26                                                      (m, 3H, 5-H, 6-H),                                                             4.45-5.60 (m, 5H,                                                              1'-H, 1-H, 2-H, 3-H,                                                           4-H)                                                       Z    1-O--(1'-methoxy-                                                                             (80 MHz, D.sub.6 -acetone/                                      butyl)-α-D-gluco-                                                                       D.sub.2 O): 0.82-1.82 (m,                                       pyranose       7H, 2'-H, 3'-H, 4'-H),                                                         3.36 and 3.42 (2s, 3H,                                                         OCH.sub.3), 3.28-3.85 (m,                                                      6H, 2-H, 3-H, 4-H,                                                             5-H, 6-H), 4.01 (s,                                                            4H, OH), 4.53-4.90                                                             (m, 1H, 1'-H), 5.02                                                            and 5.08 (2d, J =                                                              3.75 Hz, 1H, 1-H)                                    1a + 2e                                                                              A    1-O--(1',3',3'-                                                                           79  (60 MHz, CDCl.sub.3):                                                                         (Film):                                          trimethoxyprop-                                                                               2.00 (s, 3H, CH.sub.3),                                                                       2950, 2920                                       yl)-2,3,4,6-   2.02 (s, 6H, CH.sub.3),                                                                       (CH)                                             tetra-O--acetyl-                                                                              2.04 (s, 3H, CH.sub.3),                                                                       2850                                             β-D-glucopyran-                                                                          1.83-2.04 (m, 2H,                                                                             (acetal)                                         ose            2'-H), 3.29 and 3.36                                                                          1750 (CO)                                                       (2s, 3H, OCH.sub.3), 3.30                                                      (s, 6H, OCH.sub.3), 3.55-                                                      3.86 (m, 1H, 5-H), 3.92-                                                       4.28 (m, 2H, 6-H),                                                             4.34-5.18 (m, 6H, 1-H,                                                         1'-H, 2-H, 3-H, 3'-H,                                                          4-H)                                                       Z    1-O--(1',3',3'-                                                                               (80 MHz, D.sub.6 -acetone/                                      trimethoxyprop-                                                                               D.sub.2 O): 1.89-2.14 (m,                                       yl)-β-D-gluco-                                                                           2H, 2'-H), 3.33 (s,                                             pyranose       6H, OCH.sub.3), 3.43 and                                                       3.45 (2s, 3H, OCH.sub.3),                                                      3.16-3.95 (m, 6H,                                                              2-H, 3-H, 4-H, 5-H,                                                            6-H), 4.12 (s, 4H,                                                             OH), 4.63 and 4.71                                                             (2d, J = 7.5 Hz, 1H,                                                           1-H), below this                                                               4.45-4.93 (m, 2H,                                                              1'-H, 3'-H)                                          1a + 2e                                                                              B    1-O--(1',3',3'-                                                                           79  (100 MHz, CDCl.sub.3):                                          trimethoxyprop-                                                                               1.92-2.14 (m, 2H,                                               yl)-2,3,4,6-   2'-H), 1.98 (s, 3H,                                             tetra-O-acetyl-                                                                               CH.sub.3), 2.00 (s, 3H,                                         α-D-glucopyran-                                                                         CH.sub.3), 2.02 (s, 3H,                                         ose (4d)       CH.sub.3), 2.06 (s, 3H,                                                        CH.sub.3), 3.26 and 3.38                                                       (2s, 3H, OCH.sub.3), 3.30                                                      (s, 6H, OCH.sub.3), 3.99-                                                      4.26 (m, 3H, 5-H,                                                              6H), 4.39-5.57 (m,                                                             6H, 1-H, 1'-H, 2-H,                                                            3-H, 3'-H, 4-H)                                            Z    1-O--(1',3',3'-                                                                               (100 MHz, D.sub.6 -acetone/                                     trimethoxyprop-                                                                               D.sub.2 O): 1.92-2.17 (m,                                       yl)-α-D-gluco-                                                                          2H, 2'-H), 3.32 (s,                                             pyranose       6H, OCH.sub.3), 3.38 and                                                       3.42 (2s, 3H, OCH.sub.3),                                                      below this to 3.82                                                             (m, 6H, 2-H, 3-H,                                                              4-H, 5-H, 6-H), 4.26                                                           (s, 4H, OH), 4.49-                                                             4.88 (m, 2H, 1'-H,                                                             3'-H), 5.02 and 5.12                                                           (2d, J = 3.75 Hz,                                                              1H, 1-H)                                             1a + 2f                                                                              A    1-O--(1',2'-di-                                                                           77  (60 MHz, CDCl.sub.3):                                           methoxyethyl)- 2.00 (s, 3H, CH.sub.3),                                         2,3,4,6-tetra- 2.02 (s, 3H, CH.sub.3),                                         O--acetyl-β-D-                                                                           2.03 (s, 3H, CH.sub.3),                                         glucopyranose  2.04 (s, 3H, CH.sub.3),                                         (3e)           3.33-3.47 (m, 8H,                                                              2'-H, OCH.sub.3), 3.56-                                                        3.89 (m, 1H, 5-H),                                                             4.07-4.36 (m, 2H,                                                              6-H), 4.70-5.21 (m,                                                            5H, 1-H, 1'-H, 2-H,                                                                        Z? 1-O--(1',2'-dime-? ? (100 MHz,      D.sub.6 -acetone/? ? ? thoxyethyl)-β-D-? ? D.sub.2 O): 3.21-3.95 (m,?      ? ? glucopyranose? ? 8H, 2-H, 2'-H, 3-H, 4-H,? ? ? ? ? 5-H, 6-H), 3.35 (s,      3H,? ? ? ? ? OCH.sub.3), 3.45 and 4.47 (2s,? ? ? ? ? 3H, OCH.sub.3), 4.18      (s, 4H,? ? ? ? ? OH), 4.57 and 4.67 (2d,? ? ? ? ? J = 7.5 Hz, 1H, 1-H),? ?      ? ? ? 4.79 and 4.94 (2t, J =? ? ? ? ? 5.5 Hz, 1H, 1'-H)? 1a + 2f? B?      1-O--(1',2'-dime-? 84? (100 MHz, CDCl.sub.3): 2.02? (Film):? ? ?      thoxyethyl)-? ? (s, 3H, CH.sub.3), 2.04 (s,? 3020, 2940? ? ?      2,3,4,6-tetra-? ? 3H, CH.sub.3), 2.06 (s, 3H,?(CH)? ? ?      O--acetyl-α-D-? ? CH.sub.3), 2.10 (s, 3H, CH.sub.3),? 2850 (acetal)?      ? ? glucopyranose? ? 3.36, 3.40 and 3.47 (3s,? 1750 (CO)? ? ? (4e)? ? 6H,      OCH.sub.3), 3.30-3.52 (m,? ? ? ? ? 2H, 2'-H), 3.98-4.37 (m,? ? ? ? ? 3H,      5-H, 6-H), 4.64-5.64? ? ? ? ? (m, 5H, 1-H, 1∝-H, 2-H,? ? ? ? ? 3-H,      4-H)? ? Z? 1-O--(1',2'-dime-? ? (80 MHz, D.sub.6 acetone/? ? ?      thoxyethyl)-α-D-? ? D.sub.2 O): 3.40-3.78 (m,? ? ? glucopyranose? ?      8H, 2'-H, 2-H, 3-H,? ? ? ? ? 4-H, 5-H, 6-H), 3.40,? ? ? ? ? 3.48 and 3.53      (3s, 6H,? ? ? ? ? OCH.sub.3), 4.52 (s, 4H,? ? ? ? ? OH), 4.72-4.96 (m,      1H,? ? ? ? ? 1'-H), 5.12 and 5.20? ? ? ? ? (2d, J = 3.75 Hz, 1H,? ? ? ? ?      1-H)? 1a + 2g? A? 1-O--(2'-chloro-? 71? (60 MHz, CDCl.sub.3): 2.03? ? ?      1'-methoxyethyl)-? ? (s, 3H, CH.sub.3), 2.06 (s,? ? ? 2,3,4,6-tetra-O--? ?      6H, CH.sub.3), 2.08 (s, 3H,? ? ? acetyl-β-D-gluco-? ? CH.sub.3),      3.45-3.98 (m, 6H,? ? ? pyranose? ? 2'-H, 5-H, OCH.sub.3), 4.20-? ? ? ? ?      4.34 (m, 2H, 6H), 4.67-? ? ? ? ? 5.23 (m, 5H, 1-H, 1'-H,? ? ? ? ? 2-H,      3-H, 4-H)? ? Z? 1-O--(2'-chloro-? ? (80 MHz, D.sub.6 -acetone/? ? ?      1'-methoxyethyl)-? ? D.sub.2 O): 3.40-3.95 (m,? ? ?      β-D-glucopyranose? ? 8H, 2'-H, 2-H, 3-H,? ? ? ? ? 4-H, 5-H, 6-H),      3.42? ? ? ? ? and 3.49 (2s, 3H,? ? ? ? ? OCH.sub.3), 3.65 (s, 4H,? ? ? ? ?      OH), 4.56 and 4.62? ? ? ? ? (2d, J = 7.5 Hz, 1H,? ? ? ? ? 1-H), 4.82 and      4.92? ? ? ? ? (2d, d, J = 7 Hz and? ? ? ? ? 3.75 Hz, 1H, 1'-H)? 1a + 2g?      B? 1-O--(2'-chloro-? 82? (100 MHz, CDCl.sub.3):? (Film):? ? ?      1'-methoxyethyl)-? ? 1.98 (s, 3H, CH.sub.3),? 2980, 2950? ? ?      2,3,4,6-tetra-O--? ? 2.01 (s, 3H, CH.sub.3),? (CH)? ? ?      acetyl-α-D-gluco-? ? 2.02 (s, 3H, CH.sub.3),? 2860 (acetal)? ? ?      pyranose (4f)? ? 2.05 (s, 3H, CH.sub.3),? 1750 (CO)? ? ? ? ? 3.37-3.59 (m,      5H,? ? ? ? ? 2'-H, OCH.sub.3), 4.01-? ? ? ? ? 4.29 (m, 3H, 5-H,? ? ? ? ?      6-H), 4.62-5.58 (m,? ? ? ? ? 5H, 1-H, 1'-H, 2-H,? ? ? ? ? 3-H, 4-H)? ? Z?      1-O--(2'-chloro-? ? (60 MHz, D.sub.6 -acetone/? ? ? 1'-methoxyethyl)-? ?      D.sub.2 O): 3.33-3.86 (m, 8H,? ? ? α-D-glucopyranose? ? 2-H, 2'-H,      3-H, 4-H,? ? ? ? ? 5-H, 6-H), 3.50 and? ? ? ? ? 3.53 (2s, 3H, OCH.sub.3),?      ? ? ? ? 4.25 (s, 4H, OH),? ? ? ? ? 4.56-5.01 (m, 1H, 1'-H),? ? ? ? ? 5.19      and 5.21 (2d, J =? ? ? ? ? 3.75 Hz, 1H, 1-H)? 1a + 2h? A? 1-O--(2'-bromo-?      78? (60 MHz, CDCl.sub.3): 2.02? ? ? 1'methoxyethyl)-? ? (s, 3H, CH.sub.3),      2.04 (s,? ? ? 2,3,4,6-tetra-O--? ? 3H, CH.sub.3), 2.06 (s, 3H,? ? ?      acetyl-β-D-gluco-? ? CH.sub.3), 2.10 (s, 3H, CH.sub.3),? ? ? pyranose      (3g)? ? 3.36-3.50 (m, 5H, 2'-H,? ? ? ? ? OCH.sub.3), 3.67-3.93 (m, 1H,? ?      ? ? ? 5-H), 4.04-4.36 (m, 2H,? ? ? ? ? 6-H), 4.73-5.26 (m, 5H,? ? ? ? ?      1-H, 1'-H, 2-H, 3-H,? ? ? ? ? 4-H)? ? Z? 1-O--(2'-bromo-? ? (80 MHz,      D.sub.6 -acetone/? ? ? 1'-methoxyethyl)-? ? D.sub.2 O): 3.30-3.95 (m,      11H,? ? ? β-D-glucopyranose? ? 2'-H, OCH.sub.3, 2-H, 3-H,? ? ? ? ?      4-H, 5-H, 6-H), 4.11 (s,? ? ? ? ? 4H, OH), 4.63 and 4.71? ? ? ? ? (2d, J =      7.5 Hz, 1H,? ? ? ? ? 1-H), 4.79-5.00 (m, 1H,? ? ? ? ? 1'-H)? 1a + 2h? B?      1-O--(2'-bromo-? 83? (100 MHz, CCl.sub.4): 2.00? (Film):? C: 42.08? 41.95?      ? ? 1'-methoxyethyl)-? ? (s, 3H, CH.sub.3), 2.02 (s,? 2960 (CH)? H: 5.19?      5.16? ? ? 2,3,4,6-tetra-O--? ? 3H, CH.sub.3), 2.04 (s, 3H,? 2840 (acetal)?      C.sub.17 H.sub.25 O.sub.11 Br? ? ? acetyl-α-D-gluco-? ? CH.sub.3),      2.07 (S,3H, CH.sub.3),? 1745 (CO)? (485.29)? ? ? pyranose (4g)? ? 3.38 and      3.46 (2s, 3H,? ? ? ? ? OCH.sub.3), 3.28-3.52 (m,? ? ? ? ? 2H, 2'-H),      3.94-4.35? ? ? ? ? (m, 3H, 5-H, 6-H),? ? ? ? ? 4.65-5.60 (m, 5H, 1-H,? ? ?      ? ? 1'-H, 2-H, 3-H, 4-H)? ? Z? 1-O--(2'-bromo-? ? (200 MHz, D.sub.6      -acetone/? ? ? 1'-methoxyethyl)-? ? D.sub.2 O): 3.42 -3.88 (m, 8H,? ? ?      α-D-glucopyranose? ? 2-H, 2'-H, 3-H, 4-H,? ? ? ? ? 5-H, 6-H), 3.50      and 3.54? ? ? ? ? (2s, 3H, OCH.sub.3), 4.53 (s,? ? ? ? ? 4H, OH), 4.89 and      4.95? ? ? ? ? (2d, d, J = 5.5 Hz and? ? ? ? ? 4.0 Hz, 1H, 1'-H), 5.19? ? ?      ? ? and 5.21 (2d, J = 3.75 Hz,? ? ? ? ? 1H, 1-H)? 1a + 2i? ?      1-O--(1'-dimeth-? ? Mass spectrum:? ? ? oxy-methyl)-6-O--? ? MS (M/e): 363      (0.4, M.sup.+? ? ? methyl-2,3,4-? ? --CH.sub.3 O), 319 (0.4, M.sup.+? ? ?      tetra-O-- acetyl-? ? --C.sub.3 H.sub.7 O.sub.2), 303 (1.3, M.sup.+? ? ?      β-D-glucopyran-? ? --C.sub.3 H.sub.7 O.sub.3), 243 (4, 303-? ? ? ose      (6)? ? C.sub.2 H.sub.4 O.sub.2), 183 (4, 243-? ? ? ? ? C.sub.2 H.sub.4      O.sub.2), 141 (14,? ? ? ? ? 183-C.sub.2 H.sub.2 O), 75 (98,? ? ? ? ?      C.sub.3 H.sub.7 O.sub.2.sup.+)? 1c + 2b? A? 1-O--(1'-methoxy-? 89? (60      MHz, CCl.sub.4): 3.34? (Film):? ? ? methyl)-2,3,4,6-? ? (s, 3H,      OCH.sub.3), 3.42-? 3105, 3080? ? ? tetra-O--benzyl-? ? 3.98 (m, 6H, 2-H,      3-H,? 3050 (CH? ? ? β-D-glucopyranose? ? 4-H, 5-H, 6-H), 4.41-?      aromatic)? ? ? (6a)? ? 4.92 (m, 11H, 1-H,? 2940, 2910? ? ? ? ? 1'-H,      CH.sub.2), 7.04-7.33? 2880 (CH? ? ? ? ? (m, 20H, C.sub.6 H.sub.5)?      aliphatic)? 1d + 2b? A? 1-O--(1'-methoxy-? ? (100 MHz, CDCl.sub.3):? 2840      (acetal)? ? ? methyl)-2,3,4,6-? ? 3.37 (s, 3H, OCH.sub.3),? 1620, 1590,? ?      ? tetra-O--benzyl-? ? 3.52-4.12 (m, 6H,? 1500 (aromatic)? ? ?      α-D-glucopyranose? ? 2-H, 3-H, 4-H, 5-H,? 740, 700 (ben-? ? ? (6b)?      ? 6-H), 4.34-5.03 (m,? zene ring,? ? ? ? ? 10H, 1'-H, CH.sub.2),?      monosubstituted)? ? ? ? ? 5.13 (d, J = 3.75 Hz,? ? ? ? ? 1H, 1-H),      7.04-7.33? ? ? ? ? (m, 20H, C.sub.6 H.sub.5)? 7 + 2b? A? Methyl      1-α-O--(1'-? 90? (100 MHz, CDCl.sub.3):? (Film):? 242.1154? ? ?      methoxy-methyl)-1,? ? 1.18-2.32 (m, 7H,? 2960, 2900? 242.1155? ? ?      4aα,5,6,7aα-? ? 5-H, 6-H, 7a-H),? 2880 (CH)? ? ?      hexahydrocyclo-? ? 2.76 (q, J = 8.0 Hz,? ? (mass spectro-? ? ?      penta(c)pyran-? ? 1H, 4a-H), 3.40 (s,? 2935 (acetal)? scopic)? ? ?      4-carboxylate? ? 3H, OCH.sub.3), 3.69 (s,? 1610 (CO)? C.sub.12 H.sub.18      O.sub.5? ? ? (8)? ? 3H, CH.sub.3), 4.59 (d,? 1630 (C═ C)? ? ? ? ? J =      6.5 Hz, 1H, 1'-H),? ? ? ? ? 4.76 (d, J = 7.5 Hz,? ? ? ? ? 1H, 1-H), 497      (d, J =? ? ? ? ? 6.5 Hz, 1H, 1'-H),? ? ? ? ? 7.39 (d, J = 1.0 Hz,? ? ? ? ?      1H, 3-H)? 

We claim:
 1. Process for the production of a 1,1'-diacetal of the formula ##STR12## in which R¹ and R² are identical or different, and each represents an aliphatic, saturated or unsaturated hydrocarbon radical having 1 to 6 carbon atoms, which is unsubstituted or substituted by 1 to 6 substituents selected from acetyl-, benzylcarbonyl-, benzyl- or trityl-protected OH, C₁ --C₄ --O--alkyl, C₁ -C₄ -alkoxycarbonyl or phenyl, or R¹ and R² represent C₁ -C₄ -alkylene which is unsubstituted or substituted by 1 to 6 substituents selected from protected OH, C₁ -C₄ -O-alkyl, C₁ -C₄ -alkoxycarbonyl or phenyl,R³ represents C₁ -C₆ -alkyl and R⁴ represents C₁ -C₆ -O-alkyl or saturated or unsaturated C₁ -C₆ -alkyl, which comprises reacting a silyl compound of the formula ##STR13## in which R¹ and R² are defined as above, and in which R⁶, R⁷ and R⁸ represents C₁ -C₈ -alkyl, with an acetal of the formula ##STR14## in which R³ and R⁴ are defined as above, and R⁵ represents C₁ -C₁₀ -alkyl, unsubstituted phenyl or phenyl substituted by halogen, nitro or C₁ -C₄ -O-alkyl, in the presence of an catalyst of the formula ##STR15## in which R⁹, R¹⁰, R¹¹, R¹² and R¹³ are identical or different and each represents C₁ -C₈ -alkyl, and X represents FSO₃, CF₃ CO₂, ClO₄, BF₄, CH₃ SO₃ or CF₃ (CF₂)_(n) --SO₃ (in which n is 0, 1, 2, 3 or 4), in a suitable solvent.
 2. A process according to claim 1, in which X represents CF₃ SO₃.
 3. A process according to any of claims 1 or 2, in which R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹² and R¹³ denote methyl radicals.
 4. A process according to claim 1, in which the reaction is carried out at a temperature between -80° C. and 100° C.
 5. A process according to claim 1, in which the solvent used is CH₂ Cl₂, CHCl₃, acetonitrile, diethyl ether or tetrahydrofuran.
 6. A process according to claim 1, in which the silyl compound of formula (II) is reacted with an equimolar amount or an excess of the acetal of formula (III).
 7. A process according to claim 1, in which about 1/10 equivalent, relative to the silyl compound of formula (II) of the catalyst of formula (IV) or (V) is added.
 8. A process for the production of 1-O-(1'-methoxy methyl)-2,3,4,6-tetra-O-acetyl-β-D-glucopyranose which comprises reacting a compound of the formula ##STR16## wherein R¹⁶ is acetyl, R¹⁵ is H andR¹⁴ is O-Si(CH₃)₃ with an acetal of the formula ##STR17## in the presence of trimethyl silyl trifluoromethane sulphonate as catalyst in a suitable solvent. 